The present invention relates to a method for the purification of air or gas streams by a multi-path adsorption principle in connection with a moving-bed filtering apparatus in which the gas streams are conducted through at least two multi-zone shifting bed adsorption stages arranged in series with one another.
In each of the filters the particle content of the gas stream is reduced to a degree which depends on the adsorption or filter bed material, the hydrostatic pressure differential which depends on the height of the filter bed and the filter bed density, the flow velocity and the filler apparatus charge which is dependent on the flow velocity and, with a continuously moving bed, the charge of the filter bed which increases in the direction of movement of the filter bed.
It has been tried to improve the filtering or adsorption process in single bed cross-flow filters to some degree by changing the bed height and in multiple bed filters by a partial subsequent filtering step. However the utilization of the filtering and adsorption materials remains unsatisfactory. It can be improved to some degree only in filter apparatus with not-continuously moving filter beds.
Baffles have been provided in elbows of ducts in order to reduce the flow resistance but such measures have failed to appreciably improve the overall filter efficiency of the filter material in a multiple path adsorption filter apparatus.
It is an object of the present invention to provide a method of purifying air or gas streams and to provide a suitable moving-bed filter apparatus with which the effectiveness of the filter or the adsorption material in the filter beds is close to the theoretical design values of the filters and this object should be achievable with continuous as well as discontinuous operation of the moving filter beds.
It is further an object of the present invention to facilitate performing of the purification method also with a moving filter apparatus including two serially arranged and vertically disposed filter chambers or stages in which the filter material of the secondary chamber or stage may be switched over to the first chamber or stage.
The present invention is applicable in connection with filtering as well as adsorption processes and apparatus and the two terms are therefore used interchangeably in the present sepcification.